Planar Light-guiding Circuits (PLCs) are optical circuits having planar optical waveguides. These PLCs play an important role in the optical industry in that many optical and electro-optical structures may be put on a single substrate, thus improving the functionality and lowering the costs of optical systems.
Some PLCs, such as optical switches, have electro-optical deflectors, which change the direction of the light propagation through the waveguide. The light is bent by using an externally applied voltage to change the refractive index of the waveguide material. The thinner the waveguide material is, the lower the voltage necessary to provide a given deflection angle. Thus to reduce power consumption and device size, the waveguide material should be made as thin as practical.
Lithium niobate (LN), i.e., LiNbO3, is typically used as the waveguide material for fabrication of PLC electro-optic deflectors. The major problem with using lithium niobate is that the LN crystals are brittle and thus traditionally could not be made thinner than 100-150 μm. Recently, the research group at Columbia University has developed a technique of Crystal Ion Slicing (CIS), which allows detachment of a LN layer as thin as 5-10 μm. However, due to the film's brittleness, there is still the problem of taking the thin detached LN film and using it in fabricating the defector. The result is that the size and power consumption of electro-optical deflectors cannot be significantly reduced.
Lithium niobate is just one of a number of ferroelectric oxide materials that can be used in making an electro-optical device. Thus the problem of using a thin brittle material as part of a device fabrication, extends to a layer of any thin ferroelectric oxide material.
Thus there is a need for a process to integrate a thin brittle ferroelectric oxide layer into the fabrication of an electro-optical device and in particular to the integration of a thin lithium niobate layer into the fabrication of an electro-optical deflector device. In addition, a thin film lithium niobate deflector device is needed.